1. Field of the Invention
The present invention relates in general to electrochemical cells, and more particularly, to a current collector having a uniformly applied lithium polysilicate primer, which serves to, among other things, enhance the electrochemical performance of the same.
2. Background Art
Secondary electrochemical cells using a primer between the active material layer and the current collector of the electrode are well known in the art. However, conventional primers have not effectively addressed the problem associated with high interfacial resistance between the active material layer and the current collector. In particular, the lack of a thin, uniformly applied primer results in inconsistent electrical contact between the current collector and the active material layer, which has detrimental consequences relative to power density and cycle life of an associated electrochemical cell. In addition, convention primers that are fabricated from compounds other than lithium polysilicates are limited in their application to one type of electrode (i.e. an anode or cathode), but not both.
It is therefore an object of the present invention to provide a current collector having a thin, uniformly applied lithium polysilicate binder, to in turn, remedy the aforementioned complications and/or detriments associated with conventionally primed current collectors.
The present invention is directed to a primed current collector for use in an electrochemical cell comprising: (a) a current collector having a first surface and a second surface; and (b) a primer applied to at least a portion of the first and/or second surfaces of the current collector, wherein the primer comprises a uniform layer of lithium polysilicate.
In a preferred embodiment of the invention, the primed current collector further comprises means associated with the primer for exhibiting a uniform current response upon application of an electrical potential.
In another preferred embodiment of the invention, the primed current collector comprises a thickness ranging from approximately 0.5 microns to approximately 3.0 microns, and more preferably from approximately 1.5 microns to approximately 2.5 microns.
It is also contemplated that the primer further comprise a carbonaceous component, such as graphite, carbon black, or mixtures thereof. In this embodiment the carbonaceous component preferably comprises approximately 50 percent by weight of the primer.
Preferably the current collector if fabricated from a metal foil selected from one of the group consisting essentially of copper, aluminum and alloys thereof and has a thickness ranging from approximately 10 microns to approximately 25 microns.
The present invention is also directed to a process for fabricating a primed current collector comprising the steps of: (a) fabricating a current collector; (b) fabricating a primer, wherein the primer comprises lithium polysilicate; (c) controllably associating the primer with the current collector; and (d) at least partially drying the primed current collector.
In a preferred embodiment of the process, the step of fabricating the primer comprises the step of combining a solvent, lithium polysilicate, and a carbonaceous component.
In another preferred embodiment of the process, the step of controllably associating the primer with the current collector comprises the step of applying a coating of primer onto the current collector, wherein the dry thickness of the coating is approximately 0.5 microns to approximately 3.0 microns thick.
It is also contemplated that the step of at least partially drying the primed current collector comprises the step of exposing the same to a forced hot air oven at approximately 180 degrees Fahrenheit.